BLOOD FLUKES 



301 



Indies, as shown by the reports of Surgeon Holcomb from Porto Rico, 

 rectal bilharziasis is rather common. In these cases the egg is prac- 

 tically always lateral-spined. Looss thinks that the lateral-spined egg 

 is the product of an unfertilized female S. hamatobium. These flukes 

 differ from other human flukes in possessing nonoperculated eggs as 

 well as in having the sexes separate. The adults of this species, the 

 S. mansoni, are scarcely, if at all, to be distinguished from the S. 

 hamatobium. Leiper has recently noted a difference in that the male of 



FIG. 67. Anatomy of a tape- worm, T&nia solium (A., longitudinal, B., cross 

 section); a fluke, Paragonimus westermanii (C)., male and female nematode, Oxyuris 

 vermicularis (D.). A. i, Testes; 2, yolk glands; 3, shell glands; 4, ovary; 5, vagina; 



6, vas deferens; 7, uterus before branching; 8, water-vascular system. B. i, Cuticle; 

 2, circular muscle; 3, ovary; 4, testes; 5, uterus; 6, excretory canal; 7, nerve cord. 

 C. i, Oral sucker; 2, acetabulum; 3, uterus; 4, testes; 5, excretory canal; 6, ovary; 



7, yolk glands. D. (a) Female, i, Vulva; 2, uterus; 3, bulb of oesophagus; 4, anus; 

 (D) Male. i. Bulbous mouth end; 2, testes; 3, spicule; 4, alimentary canal. E. 

 Egg. of P. westermanii. 



S. mansoni has seven testicles as against four for S. hamatobium. With 

 S. japonicum, the name of the Eastern species, there is not only the 

 difference that the eggs are without spines, but, in addition, the skin 

 of the adult parasite is not tuberculated, as is the case with the other 

 two species. It is slightly smaller, the acetabulum projects more 

 prominently, and the lower part of the male infolds more markedly 



